Single embryo transfer: a mini-review.

This paper provides a concise review of single embryo transfer (SET) in cycles using fresh embryos as well as in cycles using frozen-thawed embryos. Relevant studies were identified by a computerized search in PubMed for the period 1995-2004. The pregnancy rates, delivery rates and multiple pregnancy/birth rates were evaluated after fresh or frozen embryo transfer as well as cumulative delivery rates after fresh and frozen SET. The results of four randomized controlled trials (RCT) and seven observational studies using fresh embryo transfers are analysed. No RCT with SET in freezing-thawing cycles was identified, while one observational study was identified. The effects of a change in the rules from the National Board of Health and Welfare in Sweden in 2003 regarding the implementation of SET in Sweden are summarized.